Internal combustion engines are maintained at operating temperatures by circulating an intermediate heat transfer fluid or coolant, such as ethylene glycol, water or the like through conduits or hoses disposed between the engine and a heat transfer assembly, commonly known as a radiator, wherein the heated coolant is passed through conduits in a core thereof and is cooled by ambient air passing through the radiator core in indirect heat tranfer relationship to the coolant flowing through the conduits. The coolant is permitted to flow through the radiator core and engine through such related conduits or hoses by the opening of a thermostat normally disposed in the internal combustion engine. Thus, coolant flow is permitted upon opening of the thermostat with the understanding the coolant flow may vary between no flow (closed) and full flow. Similarly, freon for air conditioning units are passed after compression through a heat exchanger to cool the compressed fluid prior to expansion into the heat exchanger through which air is passed in cooling heat transfer relationship.
Generally, to effect a flow of air through the radiator core sufficient to effecting cooling of the coolant, a fan assembly including at least a four blade fan configuration is provided on the engine side of the radiator to draw air therethrough, rotation of the fan blade being directly related to the RPM's of the internal combustion engine. Thus, the slower the RPM's of the engine, the slower is the rotation of the fan resulting in a smaller quantity of forced air flow.
In copending application Ser. No. 159,589 filed July 16, 1980, there is disclosed a fan assembly for a radiator comprised of a fan driven by an electric motor and formed of two blades of the axial flow, propeller type S-configuration wherein the radiator is disposed in a conventional manner forward of the automobile engine.
Compaction of the automobile has required relocation of the heat exchange or radiator from such conventional position to alternate positions consistant with reasonable fluid flow conditions for the intermediate heat transfer fluid. Thus, the radiator may be mounted aside the motor, i.e. perpendicular to the conventional position, or in some other location on the vehicle. While the fan assembly of the aforesaid copending application is adequate where natural convection condition's effect a heat transfer relationship or a result of the velocity of the vehicle, alternate mounting of the heat exchanger or radiator necessitate a more positive flow of cooling air through the heat exchanger or radiator.
Hydraulic fan assemblies have found some usage and have been associated with an electrically or air operated flow divider. Flow dividers are very expensive and are constantly working under high pressures. When operation of the fan is required, the flow divider is closed thereby starting the fan motor. In such a system, the hydraulic pump is constantly being turned by the engine thereby wasting energy and causing unnecessary wear and tear on the hydraulic pump. Additionally, such type of system requires a by-pass line to a reservoir to recycle hydraulic fluid since the hydraulic pump is in constant operation. Consequently, since the hydraulic pump is in constant operation, a heat exchanger is required to cool the hydraulic fluid.